OBJECTIVETo investigate the function of a novel biosensor used for the rapid determination of biochemical oxygen demand (BOD) which is developed by our research group based on suspended immobilized microbial cell system in a completely mixed determining chamber as a substitute of the traditional membrane system.

METHODSActivated sludge was immobilized by PVA gel and used as a bio-sensing element. The novel biosensor was used to measure the short time BOD value and the conventional cultivation method was used for BOD5 measurement.

RESULTSA linear relationship was observed for the difference between the current and the concentration of glucose-glutamic acid (GGA) solution below 200 mg/L with a correlation coefficient of 0.995. The optimal response of the sensor was obtained at pH 7.0 and 30 degrees C. The sensor response was within 15 min and was reproducible within +/- 5% of the mean in a series of eight samples containing 75 mg/L BOD using standard GGA solution. The novel sensor response was found to be fairly constant over a period of 30 days, with +/- 5% fluctuations.

CONCLUSIONA relatively good agreement is found between BOD estimated by the novel BOD biosensor and that determined by the conventional 5-day BOD method. This novel BOD biosensor has good sensitivity, stability and reproducibility.

Biosensing Techniques ; Boric Acids ; chemistry ; Glucose ; metabolism ; Glutamic Acid ; metabolism ; Oxygen ; analysis ; metabolism ; Polyvinyl Alcohol ; chemistry ; Reproducibility of Results ; Sewage ; microbiology ; Temperature

The effect of content of acid boric on Stevia rebaudiana Bectoni, being grown in Vietbac of Vietnam has been investigated. The experimental results shown that the mitable content of acid boric is 0.005% and it may be used for production of this kind of plant in Vietbac of Vietnam.
Boric acid ; Stevioside ; Growth & development ; Soil

The author carried out a study on the effectiveness of the boric acid as a stomach poison for German cockroach control from July to September 1971. The test was performed by the feeding method under conditions of 20 C and 80 per cent relative humidity. The baits were composed of one control group and five different combination groups with boric acid and sugar as follows. 10 g sugar only(control group), 1 g powedered boric acid to 9 g sugar(1:9 poison baits), 2 g powdered boric acid to 8 g sugar(2:8 poison baits), 4 g powdered boric acid to 6 g sugar(4:6 poison baits), 5 g powdered boric acid to 5g sugar(5:5 poison baits), 10 g powdered boric acid only (10:0 poison baits). The insects were composed of 360 female adult German cockroaches collected by traps at the kitchens of restaurants and house holds in Seoul City. The results were as follows: The total mortality by poison baits in 72 hours after treatment were: 44.3 per cent by 1:9 poison baits , 79.4 per cent by 2: poison baits , 96.7 per cent by 4:6 poison baits(the most effective poison baits), 88.3 per cent by 5:5 poison baits, 91.1 per cent by 10:0 poison baits. The peak mortality by the treatment hours were: Up to 21 hours: 23.3 per cent by 5:5 poison baits, 20.0 per cent by 10:10 poison baits, From 24 to 48 hours: 71.1 per cent by 4:6 poison baits, 55.6 per cent by 10:0 poison baits, From 48 to 72 hours: 21.9 per cent by 2:8 poison baits, 19.6 per cent by 1:9 poison baits. The most effective treatment hours was from 24 to 48 hours.
parasitology-arthropoda-cockcroach ; Blattella germanica ; chemotherapy ; boric acid